The ALPINE observations focus on C\(^+\) , which is an important cooling line and, therefore, expected to be prevalent in star-forming galaxies. This is especially the case at high redshifts where average SFRs are increased compared to the local universe. Correspondingly, C\(^+\)  is related to the SFR, as demonstrated in large samples of low-redshift galaxies (e.g., [1]}, [2]}). Starting in the early years of ALMA, several studies have shown that it is possible to measure C\(^+\)  out to high redshifts, although such studies mostly focused on bright submillimeter galaxies and only small samples of main-sequence galaxies [3]}, [4]}, [5]}, [6]}. The origin of C\(^+\)  emission is complicated, which could affect its relation to star formation especially at high redshifts, where star formation is taking place in environments with different chemical and radiation properties compared to low-\(z\) . While C\(^+\)  is often emitted from photo-dissociation regions (PDRs) of molecular clouds, it can also originate from the cold neutral medium and H II regions [7]}, [8]}, [9]}, [10]} or traces the diffuse ionized gas [11]}, [12]}. Furthermore, some earlier studies suggested a C\(^+\) -deficit (with respect to far-IR luminosity) in high-redshift galaxies (e.g., [13]}, [14]}, [15]}), which could be due to absolutely lower Carbon levels, observations missing broad spatial components of C\(^+\)  emission, or simply selection effects. The multiwavelength information (and especially the far-IR continuum emission) from ALPINE provides the first verification of the relation between SFR and C\(^+\)  emission at these redshifts.
